1. Field of the Invention
The present invention relates to a method and to an apparatus for separating and transporting flexible two-dimensional (sheet-like) products.
2. Description of the Related Art
Various methods and devices for separating labels and individual sheets and for their subsequent further transport are known from the state of the art, amongst other things under the description feeding devices. Such feeding devices for individual sheets, as a rule, are designed such that they pull off an individual product from a stack of sheets with suction elements and/or grippers, and then convey these individual products to a transfer location where a further working step can be carried out. Such feeding devices, as a rule, are optimized for the processing of a specific product and can not be applied to other products or within any context of the machine without modification.
The present invention in particular is envisaged for separating adhesive-coated labels which can be released from one another and for transporting them and for solving those technical particularities and difficulties which these products entail. Since 1980, self-sticking, re-releasable labels or pieces of paper (“self-adhesive notes” or paper sheets having an adhesive backing) have been on the market and have been used for various purposes, amongst others under the trademark description POST-IT®.
WO 96/39331 relates to an apparatus for attaching self-adhesive labels from a label dispenser, in which labels are transferred from a dispenser roller onto moving products by a drum provided with a radially projecting transfer element. The take-over and dispensing of the labels is effected by controlling vacuum grippers provided at the peripheral ends of the transfer element. The individually seized labels are transported tangentially away from the respective dispenser tape. A precise, reliable and gentle separation of stacked labels is not specified.
EP 0 988 246 relates to a stack holder for accommodating self-adhesive, re-peelable product supplements. Separators (plate-like slides, blow nozzles) are provided on the lower side of the stack holder to peel away individual product supplements. The adhesive-free part of a product supplement is moved perpendicularly away from the following product supplement, and the product supplement is subsequently separated by a rotating drum and is pulled off parallel to the plane of the sheet and essentially tangentially, as in the case of WO 96/39331. In contrast to WO 96/39331, the labels here are held during the conveying by clamping grippers instead of vacuum grippers.
A further feeding device is referred to in CH 684 589 which permits supplements to be deposited onto printed sheets by an adhesive. In contrast to the two above-mentioned references, the supplements (or printed sheets), during their conveying, are provided with adhesive only after their separation. A rotating conveyor drum with several planetarily driven catch drums mounted on the periphery of the conveyor drum is provided. Again, the peeling-away of the sheets is effected parallel to their side surfaces with respect to the catch drum, that is, a tangential removal of the printed sheets from the stack. This device, due to the addition of an adhesive during transport as well as the required size of the catch drum which must be matched to the product size demands a large overall design. Furthermore, the addition of an adhesive during transport is quite complicated with regard to technology and demands cycle time and leads to additional maintenance expenses.
A further solution for supply labels is referred to in EP 0 897 871. Here, labels are transferred from a punched tape sheet. The labels must be separated long before their take-over by rotating vacuum grippers and must be provided with an adhesive during the rotation movement so that they can be deposited onto corresponding products. Two other devices which although being different with regard to design, correspond to this label transfer principle are further referred to in German published application DE 28 43 418 and U.S. Pat. No. 4,293,365. These devices however in each case take the labels from a stack. With both devices, in each case, the labels taken from the label stack by rotating label carriers are transported past an adhesive depositing device and then deposited onto the associated product.
The devices discussed above each have one or more of the following disadvantages: inasmuch as the deposition of the adhesive is not effected until the transport path from the label dispenser to the dispensing location, one must accept disadvantages with regard to the cycle time, additional maintenance expenses and larger construction sizes. The separation and the taking of the products to be transferred, specifically labels, has only been solved for products free of adhesive, wherein here one must accept the limitations of the stack holder (the taking only being possible on the upper side of the stack, a limitation of the stack height, complicated control or separation elements). Inasmuch as adhesive-coated labels or products are to be separated, one must anticipate particular qualities with regard to the dispenser medium (dispenser rollers and likewise), or the taking of the product from the stacks is unreliable or possible only with restrictions.
Specifically, with EP 0 988 246, a separation by the separation element can no longer be ensured in a reliable manner when it comes to large stacks, and the forces which are required for the further transport are greatly dependent on the contact pressure on the lowermost product supplement. Depending on the applied adhesive, its properties as a result of the shear movement on removal of a product supplement can lead to a compromising of the product (smudging, formation of creases, deposits) or a disadvantageous impairment of the adhesive location itself (in particular, a shearing-away or regional release of the adhesive). Accordingly, complicated regulating and control elements, and where necessary additional sensor devices, are required. With adhesive regions having a larger area, the separation is no longer possible at all or is only possible with very small intermediate stacks having a limited contact pressure.
An apparatus for the transport of printed products is referred to in EP 1 086 914 of the assignee of the present application, which separates such products from a stack with support elements and holding members which rotate about an axis and which are supported by a separating member, thereby separating a printed product from a stack lying below the support elements and transporting it to a dispensing location. In contrast to the above-mentioned references, this solution has a fundamentally different separating principle which is significantly more reliable and can also separate adhesive-coated printed products in a quick and accurate manner without any drawbacks. This device, however, is subject to a disadvantage inasmuch as the supply of the stack is effected from below, and an additional expense with regard to control technology and design arises if the separating and conveyor element are not designed as separate elements or the supply of the stack is to be arranged at another location.